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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b10sm4629437pfi.122.2021.07.27.13.59.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 13:59:05 -0700 (PDT) From: Kees Cook To: linux-hardening@vger.kernel.org Cc: Kees Cook , "Gustavo A. R. Silva" , Keith Packard , Greg Kroah-Hartman , Andrew Morton , linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH 05/64] skbuff: Switch structure bounds to struct_group() Date: Tue, 27 Jul 2021 13:57:56 -0700 Message-Id: <20210727205855.411487-6-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210727205855.411487-1-keescook@chromium.org> References: <20210727205855.411487-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3898; h=from:subject; bh=zDRFvFHICr3CPhHUYpPjYfgsT3sRvZztC648O8M/Z+4=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhAHOBpvR1C53LhaWwxonGRaK5/85L2Hs7G8ZVB/N6 FPHA+JWJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYQBzgQAKCRCJcvTf3G3AJq8YEA Cme+/3zGc1ol3V7MYHOv02AJS8eYSYvP56YPTN+IWhbG/R9iao0T79B3njP05AdYDQ/YzSVZFyf/nM dA48kevzTJQ5BH6U98ciGMAoiY4MhSCxDjxpggkoOLHCkKWSmCLxIFysdAaSpZoavbJiYSBCDvceLN RiDHeuN7xznxcDnJd55tsJ+s4n3qET0tTBt0l2kGnVjwvTSyzmILuKrvcWemv1D0RVYiX+E2jt99TI xBdZECNgLTvRPfaECNOE/oYadRe/oj4m0V1SGwAAc25mY74Wuw87dVvp6r6XamWTMVynN4sRe1Au0l ZqV6k+AJMT52RN/mXQfd19TzgH+9eLex0ywIpeVu7Wc7KOxzgkA7tN9HjgNuY4CRUVFKbPReaMQdus vwUmDgDCcu9Dx0l4QzTYz361oipSEVY20vjIwEsR6yog6nyRGOYLp1uAmwh9xz2Kp3fv2XoaAzZXR2 I0ceyOT34//v3kbI8cZDJ0fHg0ntu/bSopVzECOxn6N5NUgkRQDKgdk28qyMDnLCU3wodi4dVaFQGS knqS45LxCRnyHOiKsBXLi2kVHORjmVCZ5fuyRrq1JDcWHgY3T3Fb/Pf8qql4TTPlb51tmVciwA7mKN nveG2L2Sw3sIt442QEpUEQ42yM7ri+HBQuuh4OsJ/a9P5DszIHRUcnJVBWcQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memcpy(), memmove(), and memset(), avoid intentionally writing across neighboring fields. Replace the existing empty member position markers "headers_start" and "headers_end" with a struct_group(). This will allow memcpy() and sizeof() to more easily reason about sizes, and improve readability. "pahole" shows no size nor member offset changes to struct sk_buff. "objdump -d" shows no no meaningful object code changes (i.e. only source line number induced differences and optimizations.) Signed-off-by: Kees Cook --- drivers/net/wireguard/queueing.h | 4 +--- include/linux/skbuff.h | 9 ++++----- net/core/skbuff.c | 14 +++++--------- 3 files changed, 10 insertions(+), 17 deletions(-) diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h index 4ef2944a68bc..52da5e963003 100644 --- a/drivers/net/wireguard/queueing.h +++ b/drivers/net/wireguard/queueing.h @@ -79,9 +79,7 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating) u8 sw_hash = skb->sw_hash; u32 hash = skb->hash; skb_scrub_packet(skb, true); - memset(&skb->headers_start, 0, - offsetof(struct sk_buff, headers_end) - - offsetof(struct sk_buff, headers_start)); + memset(&skb->headers, 0, sizeof(skb->headers)); if (encapsulating) { skb->l4_hash = l4_hash; skb->sw_hash = sw_hash; diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f19190820e63..b4032e9b130e 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -800,11 +800,10 @@ struct sk_buff { __u8 active_extensions; #endif - /* fields enclosed in headers_start/headers_end are copied + /* Fields enclosed in headers group are copied * using a single memcpy() in __copy_skb_header() */ - /* private: */ - __u32 headers_start[0]; + struct_group(headers, /* public: */ /* if you move pkt_type around you also must adapt those constants */ @@ -920,8 +919,8 @@ struct sk_buff { u64 kcov_handle; #endif - /* private: */ - __u32 headers_end[0]; + ); /* end headers group */ + /* public: */ /* These elements must be at the end, see alloc_skb() for details. */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index fc7942c0dddc..5f29c65507e0 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -987,12 +987,10 @@ void napi_consume_skb(struct sk_buff *skb, int budget) } EXPORT_SYMBOL(napi_consume_skb); -/* Make sure a field is enclosed inside headers_start/headers_end section */ +/* Make sure a field is contained by headers group */ #define CHECK_SKB_FIELD(field) \ - BUILD_BUG_ON(offsetof(struct sk_buff, field) < \ - offsetof(struct sk_buff, headers_start)); \ - BUILD_BUG_ON(offsetof(struct sk_buff, field) > \ - offsetof(struct sk_buff, headers_end)); \ + BUILD_BUG_ON(offsetof(struct sk_buff, field) != \ + offsetof(struct sk_buff, headers.field)); \ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) { @@ -1004,14 +1002,12 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) __skb_ext_copy(new, old); __nf_copy(new, old, false); - /* Note : this field could be in headers_start/headers_end section + /* Note : this field could be in the headers group. * It is not yet because we do not want to have a 16 bit hole */ new->queue_mapping = old->queue_mapping; - memcpy(&new->headers_start, &old->headers_start, - offsetof(struct sk_buff, headers_end) - - offsetof(struct sk_buff, headers_start)); + memcpy(&new->headers, &old->headers, sizeof(new->headers)); CHECK_SKB_FIELD(protocol); CHECK_SKB_FIELD(csum); CHECK_SKB_FIELD(hash); -- 2.30.2